This invention relates to new activated and recyclable ruthenium-based catalytic complexes as well as a method for synthesis of same.
The invention also relates to the use of such catalytic complexes for olefin metathesis.
The development of recyclable or activated ruthenium-based catalytic complexes is based on the work of R. Grubbs of the University of California (USA) relating to the ruthenium complex 2a (precatalyst 2b) called the Grubbs II catalyst.

Thus, the first recyclable complex 3a (precatalyst 3b) with a styrenyl ether ligand (called a “boomerang” ligand) was described by Hoveyda of the University of Boston (USA).

This compound is described in particular in the international patent application WO 0214376.
A first advantage of this complex is that it enables recycling of the precatalyst, which is recovered at the end of the reaction and can be reused.
However, this catalyst has the disadvantage of leading to significant losses, in an amount of 10% per cycle.
A second advantage of this complex is that it minimizes the presence of toxic metal residue (ruthenium) in the reaction products.
However, this complex is less active than the Grubbs 2b complex described above.
The first activated complex 4 was described in 2002, based on the electronic effect produced by the presence of a nitro group (NO2) on the Hoveyda styrenyl ether ligand described above.

This activated complex is described in the international patent application WO 2004 035596.
The activation of this precatalyst is based on the significantly accelerated detachment of the styrenyl ether ligand, which causes a rapid initiation of the catalytic cycle and therefore a significant increase in the reaction kinetics. The reactions can then take place under gentler conditions, in practice at room temperature, and with lower catalytic loads.
However, this complex is not easily recycled, and thus leads to significant toxic metal residue (ruthenium) contamination in the reaction products. Such a disadvantage is particularly detrimental to the synthesis of certain high added value products such as pharmaceutical molecules.
According to the prior art, it therefore appears that reactivity and recycling of such ruthenium complexes are two antinomic properties since, in practice, the increase in the activity is achieved at the expense of the recycling, and, conversely, the increase in recycling is achieved at the expense of the reactivity of the catalytic species.